Special thanks to Brent Blanchard at Protec Documentation Services for all his help with this article.
You can demolish a stone wall with a sledgehammer, and it's fairly easy to level a five-story building using excavators and wrecking balls. But when you need to bring down a massive structure, say a 20-story skyscraper, you have to haul out the big guns. Explosive demolition is the preferred method for safely and efficiently demolishing larger structures. When a building is surrounded by other buildings, it may be necessary to "implode" the building, that is, make it collapse down into its footprint.

Photo courtesy ImplosionWorld.com
The Barkway Court Towers in London, England: The building was blasted by Controlled Demolition Group, Ltd. in February 2000.

In this edition of HowStuffWorks, we'll find out how demolition crews plan and execute these spectacular implosions. The violent blasts and billowing dust clouds may look chaotic, but a building implosion is actually one of the most precisely planned, delicately-balanced engineering feats you'll ever see.

A Real Implosion?
Strictly speaking, an implosion is an event where something collapses inward, because the external atmospheric pressure is greater than the internal pressure. For example, if you pumped the air out of a glass tube, it might implode.

A building implosion isn't truly an implosion -- atmospheric pressure doesn't pull or push the structure inward, gravity makes it collapse. But the term implosion is in common use for this sort of demolition. In this article, we use the word this way.